Lesson D5: Forces at Work

Key Ideas   Unit Checklist

  Video Lesson

What are forces and how do they work? Watch the video below to learn more about forces and the factors that affect forces.

  Lesson D5: Forces at Work


Figure D.2.5.1 – When done properly, weightlifting can contribute to a healthy, strong body.

Figure D.2.5.2 – Naim Süleymanoğlu on a stamp – weightlifting is a popular Olympic sport.

Amazing Weightlifters

To lift an object, a person must pull the object upwards, working against the force of gravity that pulls downward. Some people can lift amazing amounts of mass. Weightlifting is an Olympic sport. An Iranian man named Hossein Rezazadeh holds the weightlifting world record as of 2015. He lifted 472 kilograms, which is the mass of a grand piano! But even stronger is a weightlifter named Naim Süleymanoğlu (fig D.2.5.2). Nicknamed "The Pocket Hercules", Naim is only 1.47 metres tall but he is considered the strongest weightlifter ever, having lifted 3.17 times his own body weight over his head, more than anyone in history. Naim is proof of the saying, "Good things come in small packages!"
Reading and Materials for This Lesson

Science in Action 7
Reading: Pages 280-284

Materials:
No other materials are required for this lesson.

 Watch More

World Champion Weightlifters

Watch this video to see Ruslan Albegov lift 464 kilograms, which is very close to the world record.




Figure D.2.5.3 – If humans were as strong as ants, we could lift trucks!

Figure D.2.5.4 – Ants can carry a surprising amount of weight.

Humans are not the only amazing weightlifters. If you have eaten a picnic outdoors, you might have seen ants carrying away food crumbs. Some ants can lift 100 times their own body weight. If humans could lift 100 times their body weight, one person could lift a heavy-duty pickup truck!

Ants can carry so much weight because they have a lightweight body structure. Because the muscles of an ant do not need to work very hard to support their own body weight, ants can use most of their muscle strength to lift heavy objects.

 Watch More

Red Fire Ants

Watch this video to learn more about the strength and other abilities of red fire ants.


  Think · Interpret · Decide

Force, Mass, and Motion: Online Simulation

This online simulation explores how motion is affected when you change the mass of objects and the amount of force applied to objects.

Click here to open the website in a new window.

Click on the box that says "Motion", as in figure D.2.5.5


Figure D.2.5.5

You will arrive at a site pictured below. On the top right-hand side of the screen is a green box with white checkboxes. Click all the blank white boxes to make checkmarks appear (see figure D.2.5.6).

Figure D.2.5.6

When you check the white boxes, you will see a speed dial and labels for kilograms appear, as in Figure D.2.5.7.

If you want to reset the simulation, click the orange circle on the top right-hand side of the screen. When you do another simulation, remember to check the blank boxes again so you can see the speed dial and the kilograms.

You can drag objects on and off the skateboard by holding the cursor with the left mouse button and dragging the object.

Figure D.2.5.7

After you have the online simulation set up, try these two simulations:

A. How does mass affect motion?
  1. Drag the fridge, one box, and the man to the skateboard. What total mass is on the skateboard?
  2. Apply 300 N by clicking the black triangle on the right-hand side of "Newtons" until you reach 300 Newtons.
  3. Observe what happens to the speed dial.
  4. Reset and try steps 1 to 3 again, but this time, drag the fridge and the box off the skateboard, leaving just the man on the skateboard.

B. How does applied force affect motion?
  1. Drag the fridge to the skateboard.
  2. Apply 50 N by clicking on the black triangle on the right-hand side.
  3. Observe what happens to the speed dial.
  4. Reset and try steps 1 to 3 again, but this time, apply 500 N.
Think • Interpret • Decide
After you have tried the simulations, consider the following questions very carefully – then, type or write your answers. After you have your answers, click the link just below the questions feedback.

Think: What's the point? Do you understand the results of this experiment? If not, try it again.
Interpret: Why did the motion of the object change with various masses when the force was the same? Why did the motion of the object change when various magnitudes of force were applied?
Decide: How does mass affect motion? How does the magnitude of an applied force affect motion?
When you apply force to a small mass, the object moves quickly. If you apply the same force to a large mass, a longer time is needed to get the mass to move. The larger the mass, the less an applied force affects the motion.

The magnitude of a force affects how quickly an object moves. If you apply a small force to an object, the object moves slowly. If you apply a large force to an object, the object moves quickly.
Measuring Force
 
Scientists use spring scales to measure force. Figure D.2.5.8 shows a variety of different types of spring scales.

To use a spring scale, hook an item to the spring and lift or pull the object. Read the scale to see how many Newtons of force you applied.
Figure D.2.5.8 – A spring scale is used to measure force in Newtons.



 Watch More

How to Use a Spring Scale

 Watch this video to learn how to use a very basic and simple science device, the spring scale.


  Think · Interpret · Decide

Force Meter Measurements

Spring scales are useful, but they do not always give an exact measurement for force, especially when measuring objects that are very similar in mass. An electronic force meter can give more accurate results.

The video below shows an experiment in which a force meter is used to measure the force needed to lift various objects. The video includes graphing. If you need to review your science graphing skills, click here .
Think • Interpret • Decide
After you have watched the experiment video, consider the following questions very carefully – then, type or write your answers. After you have your answers, click the link just below the questions feedback.

Think: Do you understand the results of this experiment? If not, watch the video again.
Interpret: Did you notice any patterns in the measurement of force for various masses? Did you notice any patterns on the graph?
Decide: What is the relationship between mass and force?

A straight line on a graph indicates a relationship between two things. In this case, the graph shows a clear relationship between mass and force. The graph indicates that, as the mass of an object increases, more force is needed to lift the object.



  Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.

Unit D Lesson 5 Self-Check

Instructions


Complete the following 6 steps. Don't skip steps – if you do them in order, you will confirm your understanding of this lesson and create a study bank for the future.

  1. DOWNLOAD the self-check quiz by clicking here.

  2. ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.

  3. COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.

  4. REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.

  5. SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.

  6. CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!


Self-Check Time!
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Self-Check Quiz Answers

Click each of the suggested answers below, and carefully compare your answers to the suggested answers.

If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.

A force is a push or a pull on an object.
The box with a mass of 1 kilogram starts moving faster. The same magnitude of force is used on both boxes, but the smaller mass has less friction working against its forward motion. This means that the smaller mass starts moving more quickly than the larger mass does.
The person who used 200 N on the ball made the ball move faster. The more force applied to an object, the more effect the force has on the motion of the object.
Force is required to move a hockey puck forward. When the player holds a hockey or ringette stick with one hand lower, he or she is able to apply more pushing force on the stick closer to the centre of gravity of the puck. If both hands are at the end of the stick away from the puck, applying the desired force would be more difficult and awkward -- perhaps impossible!
The use of a ramp to lift boxes involves changing the direction that the force is applied. Lifting a box straight up means gravity works directly against the lifting force. Putting the box on wheels on a ramp does not change the force of gravity, but it does divide it into two parts. Some of the gravity holds the box against the ramp, and some of the gravity makes the box want to roll backward down the ramp. To get the box up the ramp, the force required to overcome the gravity that makes the box roll backward is less than the amount required to lift it straight up.